Rotating biological aquarium filter system

ABSTRACT

An aquarium filter system having a rotatably mounted filter body. The filter body is structured such that when mounted with a portion of the filter body submerged in moving water, rotational movement is imparted to the filter body by the moving water. As a result of the rotational movement, at least a portion of the filter body is alternately exposed to the water and the atmosphere. This fosters the growth of aerobic bacteria on the surface of the filter body. The aerobic bacteria reduces the level of toxins within the aquarium water.

This is a division of application Ser. No. 08/004,678 filed on Jan. 14,1993, now U.S. Pat. No. 5,423,978, application Ser. No. 07/535,905,filed on Jun. 11, 1990, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to aquarium filter systems, in particular,to aquarium filter systems having rotating biological filter elements.

2. Description of Related Art

Under ideal conditions, a home aquarium will act as a substantiallyself-contained ecosystem. That is, except for the need of the aquariumoperator to provide food to the fish within the aquarium, the idealaquarium should maintain itself as an environment suitable to sustainand foster the healthy growth of the aquatic life which it contains.However, the aquatic life within the aquarium will typically releasewastes and other byproducts into the aquarium water. In time, thebuildup of undesirable wastes and pollutants can reach toxic levels andeventually poison the aquatic life within the aquarium. As a result, itis necessary for an aquarium to include a system for filtering andpurifying the aquarium water to eliminate undesirable wastes and toxinsand to maintain a healthy environment.

Typical aquarium filters rely on mechanical filtration to removedetritus from the aquarium water. Such a mechanical filter can be one ofseveral types. For example, in under gravel type filtration systems, apump circulates the aquarium water through a bed of gravel supported ona suitable structure. The gravel bed, which is typically located withinthe aquarium, traps and removes solid wastes and detritus from the wateras it flows through the bed. In other mechanical filtration systems, apump removes aquarium water from the aquarium and circulates the waterthrough a filter element and back into the aquarium. Like the gravelbed, the filter element traps and removes harmful detritus from thecirculating aquarium water.

In addition to mechanical filtration, chemical filtration can be used tomaintain a healthy, life-supporting environment within an aquarium.Chemical filtration systems typically circulate the aquarium waterthrough a chemical filter element, such as activated carbon. This typeof filtration is helpful in removing dissolved organic compounds andcarbon dioxide and can help to maintain a stable pH within the aquarium.

However, neither mechanical nor chemical filtration techniques aretypically effective in removing such waste byproducts as ammonia,nitrites, or nitrates. Some of these nitrogen based contaminants,particularly ammonia, can be extremely harmful to the types of aquaticlife typically found in aquariums. An effective method of removing suchcontaminants is biological filtration. Biological filtration relies onthe presence of aerobic bacteria to convert some water born toxicwastes, particularly ammonia, to nontoxic or less toxic substances. Itis possible for aerobic bacteria to grow, to a limited extent, onmechanical filter elements. Thus, there may be some biologicalfiltration along with the mechanical filtration described above.

However, typically, the aerobic bacteria which grows on the mechanicalfilter elements, or the under gravel bed, must rely on the dissolvedoxygen present in the water for its growth. As a result of the limitedavailability of oxygen, coupled with reduced water flow as the filterbecomes plugged, the amount of aerobic bacteria, and hence the degree ofbiological filtration, associated with mechanical filter elements orunder gravel beds is inherently limited. Further, as mechanical filterelements become plugged with detritus they must be replaced in order tomaintain water flow. Each time a filter element is replaced, any aerobicbacteria which may have colonized the filter element are removed fromthe aquarium and the colonization must restart on the new filterelement. During the recolonization period, the environmental balancewithin the aquarium may be jeopardized by the absence of sufficientamounts of aerobic bacteria.

Trickle filters have been devised as one method of fostering the growthof aerobic bacteria and increasing the efficiency of the biologicalfiltration process. In trickle filters, water is typically removed fromthe aquarium and allowed to trickle over a bed of lava rock, plasticballs, or the like. Because the filter bed is not submerged, there ismore oxygen available for the growth of aerobic bacteria. However,trickle filters can take up a relatively large area and usually requirededicated plumbing and pump fixtures. As a result, such filters can beexpensive and impractical in most applications and are not particularlyuseful for the average home aquarium.

Large scale wastewater treatment facilities frequently use rotatingbiological contactors in an effort to promote the growth of aerobicbacteria. Rotating biological contactors typically include a number ofpartially submerged filter elements, frequently disc shaped, mountedalong a central shaft. The central shaft is driven to rotate theelements such that at least a portion of each filter element isalternately submerged and exposed to the air. In this manner, the growthof aerobic bacteria on the surface of the filter elements is promoted bythe intermittent exposure to the oxygen in the air and the biologicalfiltration of the wastewater is promoted by the intermittent submersionof the bacteria bearing surfaces. However, rotating biologicalcontactors from wastewater treatment facilities are not readilycompatible for use with home aquarium systems. In part, this is due totheir large size, the need for a separate drive mechanism, and the lackof an appropriate location for such a device within the aquarium.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide anaquarium filter system which effectively reduces the quantity of toxicsubstances, particularly ammonia, in aquarium water.

A further object of the invention is to provide an aquarium filtersystem which is reliable and easily manufactured.

Another object of the invention is to provide an aquarium filter systemwhich is compact, easy to install, and simple to use.

In accordance with these and other objects, an aquarium filter system inaccordance with the present invention comprises a rotatably mountedfilter body. The filter body is structured such that when mounted with aportion of the filter body submerged in moving water, rotationalmovement is imparted to the filter body by the moving water, therebyexposing at least a portion of said filter body alternately to the waterand the atmosphere.

Other objects and aspects of the invention will become apparent to thoseskilled in the art from the detailed description of the invention whichis presented by way of example and not as a limitation of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a filter system in accordance with a preferred embodimentof the present invention.

FIG. 2 is a partially exploded view of the embodiment of FIG. 1.

FIG. 3 shows an alternative embodiment of the filter body from thesystem of FIG. 1.

FIG. 4 shows a filter system in accordance with an alternative preferredembodiment of the present invention.

FIG. 5 shows the filter body of FIG. 4.

FIG. 6 is a partially exploded view of the filter body of FIG. 2.

FIG. 7 is a module of a filter body in accordance with anotherembodiment of the invention.

FIG. 8 is a module of a filter body in accordance with anotherembodiment of the invention.

FIG. 9 is a module of a filter body in accordance with anotherembodiment of the invention.

FIG. 10 shows a filter system in accordance with another embodiment ofthe invention.

FIG. 11 shows the embodiment of FIG. 10 with the filter system lidpivoted to the open position.

FIG. 12 shows another embodiment of the rotating biological filterelement in another embodiment of the filter system.

FIG. 13 shows a top view of the embodiment of FIG. 12.

FIG. 14 shows another embodiment of a filter system in accordance withthe present invention.

FIG. 15 shows a side view of the embodiment of FIG. 14.

FIG. 16 shows a further embodiment of a filter system in accordance withthe present invention.

FIG. 17 shows a side view of the embodiment of FIG. 16.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

An aquarium filter system in accordance with a preferred embodiment ofthe present invention is indicated in FIG. 1 as reference numeral 20. Inthe illustrated filter system 20, water is drawn from the aquarium 22and into the rear portion of a filter box 24 through an intake tube 26by an impeller assembly (not shown). The aquarium water then flowsthrough the mechanical filter cartridge 28 (seen best in FIG. 2), intothe front portion of filter box 24, and over the discharge lip 30 backinto the aquarium. A biological filter element 32 is rotatably mountedover the discharge lip 30 and partially submerged within the flowingaquarium water. The flowing aquarium water impinging on the biologicalfilter element 32 causes the biological filter element 32 to rotate,alternately exposing a portion of the biological filter element to theair and the aquarium water to foster the growth of aerobic bacteria onthe surface of the biological filter element and to bring the aerobicbacteria into contact with the aquarium water. In this manner, theaerobic bacteria on the surface of the biological filter element canremove toxins, including ammonia, from the aquarium water.

As best seen in FIG. 2, the biological filter element 32 includes afilter body 33 mounted on a shaft 38. The filter body 33, is a turbineformed from a pleated sheet 48 of porous filter material held in acylindrical shape between two disks 50. The pleats 52 each extendradially from the center of the cylinder and axially between the disks50 to serve as paddles. The disks 50 may be of molded elastomeric orpolymeric material and may be formed with a stub shaft 38 extendingoutwardly therefrom. Alternatively, as seen in FIG. 3, each disk 50 maybe provided with an aperture 54 for receiving a central shaft 38. It isalso possible to use extruded porous polymer or injection molded porouspolymer instead of the pleated sheet 48.

As illustrated in FIGS. 1 and 2, the biological filter element 32 isdisposed above the discharge lip 30 of a power filter system. In theillustrated embodiment, a saddle 40 is provided to support thebiological filter element. The saddle 40 is shaped to straddletriangular elements 31 on each side the discharge lip 30. Each end ofthe saddle is provided with a retaining recess 29 into which a bearing35 is snap fit. Each bearing 35 is provided with an aperture 37 forreceiving an end of shaft 38. The aperture 37 is sized so as to allowfree rotation of the shaft 38 therein. Each retaining recess 29 isconfigured to loosely support the bearing 35 after it has been snappedinto place so as to allow the bearing to align itself with the shaft 38.In this manner the filter body 33 is rotatably suspended above thedischarge lip 30.

The filter body 32 is suspended with only a slight clearance,approximately 0.03-0.06 inches in the illustrated embodiment, above thedischarge lip 30. As a result, water flowing over the discharge lip 30and back into the aquarium impinges on the filter body, causing thebiological filter element to rotate. Because of the configuration andlocation of the filter body, the filter system of the present inventiondoes not require a separate drive means for the rotating biologicalfilter element. This substantially reduces the cost and complexity ofthe filter system and makes it ideal for use by the aquarium hobbyist.

The slight clearance between the filter body 33 and the discharge lip30, also allows for filter body 33 to be submerged to the maximum depthwithin the flowing water. Ideally, the filter body and the discharge lipshould be dimensioned such that in normal operation approximately 40-50%of the biological filter element is submerged, or wetted, at any timeand substantially all of the biological filter element is alternatelyexposed to the atmosphere and the water. This utilizes substantially theentire surface of the biological filter element for the growth ofaerobic bacteria and maximizes the contact of the aerobic bacteria withboth the impinging water and the atmosphere.

In the embodiment of FIGS. 1 and 2, the saddle 40 can be easily removedfrom the discharge lip 30. This allows for simple removal of thebiological filter element during maintenance of the other elements ofthe filter system and also allows for easy adaptation and installationof the rotating biological filter element for use in existing powerfilter systems. However, it should be understood that there are avariety of other satisfactory methods, some of which are describedsubsequently, for mounting the biological filter element within anaquarium filter system. Accordingly, the scope of the present inventionshould not be limited by those methods expressly described herein.

In an alternative embodiment, illustrated in FIGS. 4 and 5, the filterbody 33 has a number of disks 34 maintained in an axially spacedrelation by paddles 36. A shaft 38 extends axially from each end of thefilter body 33. In the embodiment of FIG. 5, the shaft 38 extendsthrough the center of the filter body 33 from one end of the filter bodyto the other. However, in other embodiments, it may be desirable toprovide a stub shaft on each end of the filter body rather than a singleshaft extending through the entire filter body.

As illustrated in FIG. 6, the filter body 33 may be modular inconstruction. In FIG. 6, each module 46 comprises a disk 34 with aplurality of radially oriented paddles 36 extending from one side of thedisk 34. An aperture 44 for receiving the shaft 38 is provided in thecenter of the disk 34. The filter body 33 is comprised of a number ofmodules received on the shaft 38. The modules may be coupled to oneanother by means of an adhesive, a snap fit, a friction fit, or anyother manner well known to those skilled in the art. Modularconstruction of the filter body can greatly simplify manufacture of thefilter body because a variety of filter bodies having differentdimensions can be produced merely by varying the number of modules andthe length of the shaft. Further, it may be easier to mold theindividual modules than to mold the entire filter body at one time.

The paddles 36 increase the efficiency of the rotation of the filterbody by the flowing water. In addition, the paddles allow for improvedbiological filtration by increasing the wetted surface area availablefor growth of the aerobic bacteria and contact with the water. Inalternative embodiments, it may be desirable to further increase thesurface area by texturing the surfaces of the modules and paddles.Although the modules of FIG. 6 each have eight uniformly spaced radiallyoriented paddles, the optimum number and orientation of the paddles mayvary depending on the particular dimensions of the biological filterbody and the discharge lip.

In some embodiments it may also be desirable to loosely pack the hubarea of each module between the shaft and the paddles with a porousfilter media to increase the surface area available for the growth ofaerobic bacteria. In other embodiments it may be desirable to have thepaddles extend all the way to the shaft.

Preferably, the structure of the filter body should be such that, incombination with the surface tension of the water, the water tends towell up into the hub area to maximize the wetted area. This isparticularly desirable in shallow water applications where the filterbody may be less than half submerged.

Alternative module configurations are shown in FIGS. 7, 8 and 9. In FIG.7, paddles 36a extend from each side of disk 34a. In FIG. 8, the paddles36b are angled slightly from the radial orientation of FIG. 6. Dependingon the direction of flow as the water moves over the discharge lip, sucha configuration may be more efficient than that of FIG. 6. In FIG. 9, amultitude of projections 36c extend perpendicularly from disk 34c. Sucha configuration greatly increases the surface area of the module.However, if the projections are spaced too closely, water may becometrapped between the projections and prevent the efficient exposure ofthe surface of the filter body to the air. It should be appreciated thatthere are a variety of other filter body and module configurations whichcould be incorporated into the biological filter of the presentinvention. It is within the contemplation of the present invention thatthe biological filter body could be made of any combination of one ormore of the possible configurations.

FIGS. 10 and 11 show an alternative embodiment of the present inventionadapted for use with a power filter system. In this embodiment, thepower filter system 20 is provided with a lid pivotally mounted alongthe top of the rear wall of the filter box 24. The front of the lid 56is provided with a cut out section in the region 58 over the dischargelip 30. The side walls 60 of the cut out region 58 are each providedwith journals 62 for rotatably receiving the ends of shaft 38. In thismanner, when the lid is closed as in FIG. 10, the biological filterelement 32 is suspended over the discharge lip 30 in a position to berotated by water flowing over the discharge lip. When the lid is pivotedto the open position, shown in FIG. 11, the biological filter element isremoved from the space over the discharge lip to allow ready access formaintenance or repair of the remaining elements of the filter system.The journals 62 can be provided with detents, or some other mechanism,to prevent the biological filter 32 from falling out when in the openposition. Alternatively, bearings of the type described above may beused in place of the journals 62. Of course, any of the alternativefilter bodies described above could be used in the embodiment of FIGS.10 and 11.

FIGS. 12 and 13 show another embodiment of the present invention adaptedfor use with a power filter system. As shown in FIG. 12, biologicalfilter element 32a includes a filter body 33a and a supporting cage 64.The filter body 32a comprises a single disk 65 with a plurality ofradially extending paddles 66. The disk 65 is centrally mounted on shaft68 which is rotatably supported by the cage 64. The cage 64 isconfigured to fit within the filter box 24 behind the filter cartridge28. The cage 64 supports the filter body 33a in a plane generallyparallel to the filter cartridge 28. As best seen in FIG. 13, thepaddles 66 are positioned such the water leaving the impeller housing(not shown) impinges on the paddles 66 to cause the filter body torotate.

The present invention can also be adapted for canister or other types offilter systems as shown in FIGS. 14 and 15. As seen in FIG. 14, theoutlet tube 70 from the canister filter system, or other type ofexternal filtration system, outlets into holding reservoir 72. Theholding reservoir 72 is provided with a discharge lip 74 similar to thedischarge lip 30 of the power filter system 20. Water within thereservoir 72 flows over the discharge lip 74 and into the aquarium. Abiological filter element 32 is positioned over the discharge lip 74such that the flowing water imparts rotational movement to thebiological filter element 32. The discharge lip 74 can straddle the edgeof the aquarium to support the reservoir 72.

In another embodiment, illustrated in FIGS. 16 and 17, the biologicalfilter element 32 is partially submerged directly in the aquarium water.The biological filter element is supported by journals 80 provided insupport brackets 76. The support brackets 76 are maintained in positionwithin the aquarium by means of hooks 78 which overhang a wall of theaquarium 22. Rotational movement is imparted to the biological filterelement 32 by water flowing from the spray bar 82 which is alsosupported by the brackets 76. The spray bar may be connected to theoutlet tube 84 of a pump or similar aquarium device. This configurationis particularly well suited for applications requiring a large filterbody because the filter body can extend substantially along an entirewall of the aquarium.

A wide variety of filter bodies have been described herein. It should beappreciated that to a large degree, these filter bodies areinterchangeable. Accordingly, the fact that a particular filter systemis illustrated using a particular type of filter body should not betaken to limit the scope of the invention in any way. Rather, thedifferent filter bodies described, as well as variations thereof, may beapplied to a large number of filter systems. The particular filter bodyfor each application is to a large degree a matter of choice and may bebased on factors such as expense, availability, ease of manufacture, andthe like. Further, submersion of the filter body to rotate and wet thefilter may be accomplished in a variety of manners, such as directing aflow of water over the filter such that it falls onto the filter orspraying a flow of water onto a portion of the filter body.

This detailed description is set forth only for purposes of illustratingexamples of the present invention and should not be considered to limitthe scope thereof in any way. Clearly numerous additions, substitutions,and other modifications can be made to the invention without departingfrom the scope of the invention which is defined in the appended claimsand equivalents thereof.

What is claimed is:
 1. A method of filtering aquarium water comprisingthe steps of:circulating the aquarium water; partially submerging arotatable filter body within the circulating aquarium water such thatthe circulating water imparts rotational movement to the filter bodyalternately exposing a portion of the filter body to the aquarium waterand the air to foster the growth of aerobic bacteria on the surface ofthe filter body.
 2. The method of claim 1 wherein the filter bodycomprises a disk shaped portion which is rotatably mounted on an axleextending through the center of the disk shaped portion.
 3. The methodof claim 2 wherein the filter body further comprises a plurality ofradially oriented blades extending from the disk shaped portion.
 4. Themethod of claim 3 wherein the rotational movement is imparted to theblades by causing the circulating aquarium water to impinge on theblades.
 5. The method of claim 1 wherein the filter body is made of aporous material, and said step of partially submerging comprisesallowing the porous material to absorb water when exposed to thecirculating aquarium water and to release the water which has beenabsorbed when exposed to the air.
 6. The method of claim 5 wherein thefilter body comprises a sheet of porous material which is pleated toprovide blades and said step of partially submerging further comprisescausing the circulating aquarium water to impinge on the blades in orderto impact the rotational movement to the filter body.
 7. The method ofclaim 6 wherein the filter body further comprises a mass of loose porousfilter material retained and enclosed by the sheet of porous filtermaterial.
 8. The method of claim 1 wherein said step of circulating theaquarium water comprises: withdrawing the aquarium water from anaquarium; and then conducting the withdrawn aquarium water in sequencepast the rotatable filter body and through a mechanical filter.
 9. Themethod of claim 8 wherein said step of conducting is carried out toconduct the aquarium water through the mechanical filter and then pastthe rotatable filter body.
 10. The method of claim 9 wherein said stepof conducting further comprises causing the aquarium water to flow overa discharge lip and, after passing the rotatable filter body, to flowback into the aquarium.
 11. The method of claim 10 wherein the aquariumwater fills the aquarium to a given level and the discharge lip islocated above the given level.
 12. The method of claim 1 wherein saidstep of circulating comprises causing the aquarium water to flow along aflow path defined in part by a discharge lip which constitutes thehighest point of the flow path, and wherein the rotatable filter body isdisposed above the discharge lip.
 13. The method of claim 12 whereinless than half of the filter body is submerged in the circulatingaquarium water.
 14. The method of claim 1 wherein less than half of thefilter body is submerged in the circulating aquarium water.
 15. A methodof biologically filtering aquarium water comprising the steps of:(a)rotating a turbine to submerge a portion of the turbine in the water ofthe aquarium; (b) further rotating the turbine to expose the turbineportion to ambient air; and (c) directing a flow of aquarium watertoward the turbine to effect rotation of the turbine to thereby cycliclyrepeat steps (a) and (b) above so as to promote the growth of aerobicbacteria on the turbine portion.